The California hazel ( Corylus cornuta subsp. californica ) is most often treated as a variey of the northern C . cornuta . The two may not be very closely related, however, differing conspicuously in habit, leaf shape, pubescence, the presence of glandular hairs, form and size of the involucre, habitat, phytogeography, and various other features (J. N. Rose 1895; J. S. Drumke 1965). A thorough taxonomic study of this group should be undertaken.